feat: add optional Laya engine mode for grouping and language detection (#12)

Add a languageDetectionMode setting (algo | laya | laya+algo) exposed
in Settings with three engine choices. When Laya is enabled, a laya
service (Dockerfile.laya, optional compose profile, models stored
outside the repo under ./data/models/laya) can be started, with model
download and deletion from the UI via /laya routes to manage disk
space. Add a channelLanguageFusion service combining Laya results
with the existing algorithm, and wire detection mode through
grouping, channel list and player. Cover engine selection, fusion
and laya service behavior with tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/js/services/channelLanguageFusion.js

@@ -0,0 +1,83 @@
+(function (root, factory) {
+    const service = factory();
+    if (typeof module === 'object' && module.exports) module.exports = service;
+    if (root) root.ChannelLanguageFusion = service;
+})(typeof globalThis !== 'undefined' ? globalThis : this, function () {
+    const LABELS = { fr: 'French', en: 'English', es: 'Spanish', unknown: 'Unknown' };
+
+    function normalizeConfidence(value) {
+        const number = Number(value) || 0;
+        return Math.max(0, Math.min(100, Math.round(number <= 1 ? number * 100 : number)));
+    }
+
+    function layaDetection(result) {
+        const rawCode = result?.language?.code || result?.language || 'unknown';
+        const code = ['fr', 'en', 'es'].includes(rawCode) ? rawCode : 'unknown';
+        const confidence = normalizeConfidence(result?.language?.confidence ?? result?.confidence);
+        return {
+            language: {
+                code,
+                label: LABELS[code],
+                confidence: code === 'unknown' ? 0 : confidence,
+                status: code === 'unknown' ? 'unknown' : confidence >= 75 ? 'high' : confidence >= 60 ? 'medium' : 'low'
+            },
+            languageScores: code === 'unknown' ? {} : { [code]: confidence },
+            languageEvidence: code === 'unknown' ? [] : [{ code, weight: confidence, type: 'laya', value: 'Local AI model' }]
+        };
+    }
+
+    function mergeHybrid(algo, result) {
+        if (!result) return algo;
+        const laya = layaDetection(result);
+        if (laya.language.code === 'unknown') return {
+            ...algo,
+            languageEvidence: [...algo.languageEvidence, ...laya.languageEvidence]
+        };
+        const combined = { ...algo.languageScores };
+        combined[laya.language.code] = (combined[laya.language.code] || 0) + laya.language.confidence;
+        const total = Object.values(combined).reduce((sum, value) => sum + value, 0);
+        const scores = Object.fromEntries(Object.entries(combined).map(([code, value]) => [code, Math.round(value / total * 100)]));
+        const ranked = Object.entries(scores).sort((a, b) => b[1] - a[1]);
+        const [code, confidence] = ranked[0];
+        const margin = confidence - (ranked[1]?.[1] || 0);
+        const certain = confidence >= 45 && margin >= 10;
+        return {
+            language: certain ? {
+                code,
+                label: LABELS[code] || code.toUpperCase(),
+                confidence,
+                status: confidence >= 75 ? 'high' : confidence >= 60 ? 'medium' : 'low'
+            } : { code: 'unknown', label: 'Unknown', confidence: 0, status: 'unknown' },
+            languageScores: scores,
+            languageEvidence: [...algo.languageEvidence, ...laya.languageEvidence]
+        };
+    }
+
+    function applyLanguageMode(algo, result, mode) {
+        if (mode === 'algo') return algo;
+        if (mode === 'hybrid') return mergeHybrid(algo, result);
+        return result ? layaDetection(result) : {
+            language: { code: 'unknown', label: 'Unknown', confidence: 0, status: 'unknown' },
+            languageScores: {},
+            languageEvidence: []
+        };
+    }
+
+    function buildLayaDescriptor(variant, variantKey, algo) {
+        const fields = [
+            ['sourceId', variant.sourceId],
+            ['name', variant.name],
+            ['groupTitle', variant.groupTitle],
+            ['sourceName', variant.sourceName],
+            ['tvgId', variant.tvgId],
+            ['algorithmScores', JSON.stringify(algo.languageScores || {})]
+        ];
+        return {
+            id: variantKey,
+            text: fields.filter(([, value]) => value !== undefined && value !== null && value !== '')
+                .map(([key, value]) => `${key}: ${value}`).join('\n')
+        };
+    }
+
+    return { applyLanguageMode, buildLayaDescriptor, layaDetection, mergeHybrid, normalizeConfidence };
+});